I believe that all manufactures will have drivetrains similar to that of the new Audi A8 fairly soon with a small motor/generator in place of the traditional alternator. There has been widespread consensus in the automotive supply chain to move to 48V systems as the number of drivetrain electric motors is rapidly increasing (suspension, engine control and even in turbochargers) this will save weight and reduce cable size, but for efficiency the power demands and surplus must be averaged out. What Audi have done is introduce a continuously engaged belt driven alternator starter motor (BAS) with a small 48V 10Ah Li-ion battery, this extends the idle-stop concept to while the car is moving. This motor can keep the car coasting for a minute or generate power while decelerating, it's also used to start the engine (except for initial cold starting when a conventional 12V Pb battery and pinion starter is used). In the Audi it's smart as it also uses the navigation system and road/traffic sensors to predict when to coast/generate/or start the ICE.
This car meets level 3 autonomy when faced with a congested dual carriageway (Tesla Autopilot is level 2; if you only need to get in the back seat it's level 5 of 5). The car's ability to understand it's environment of approaching cyclists along the kerb or weaving in front, white line motor bikes, cars approaching perpendicularly etc. is quite awesome (and a few bits of it are British). The variety of ultrasonic, optical, infra red and laser sensors enable the car to build a very detailed picture of kerbs, white lines, vegetation, and lifeforms.
One other factor leading towards autonomy is the recent ratification of the V2x wireless protocol (vehicle to everything), this will enable cars to broadcast data up to 500m. Listeners may be other cars, traffic control systems etc. For example if a car performed hard braking, listeners behind can take appropriate action, it would also enable cars to convoy more effectively, plus the vehicle mode could respond to environmental inputs such as air quality zones.
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TG